gnark-simple-verifier

A Gnark (Go) implementation of the Simple Verifier ZK circuit - a multi-handler verifier supporting various data operations with zero-knowledge proofs.

Overview

This circuit implements a multi-handler verifier that supports:

• MERKLE16_ORDERED: 16-ary Merkle tree root computation with mask
• COUNT: Count valid rows
• SUM_COL: Sum a specific column with row mask
• SUM_COL_BY: Sum column X grouped by column Y (returns array of groupSums)

Project Structure

gnark-simple-verifier/
├── main.go              # CLI entry point & benchmark
├── go.mod               # Go module
├── .gitignore           # Git ignore rules
├── README.md            # This file
├── benchmark/           # Benchmark results
│   └── BENCHMARK_REPORT.md
└── pkg/
    ├── lib/             # Library utilities
    │   ├── constants.go # Circuit parameters
    │   ├── utils.go     # Selector, Mask, LessThan
    │   ├── poseidon.go  # Poseidon2 hash (BN254 workaround)
    │   └── ssz.go       # SSZ Key-Value encoding
    ├── operators/       # Circuit operators
    │   ├── count.go     # COUNT operator
    │   ├── merkle16.go  # 16-ary Merkle tree
    │   ├── sum.go       # SUM_COL operator
    │   └── sum_by.go    # SUM_COL_BY + validation
    └── circuit/         # Main circuit
        └── circuit.go   # SimpleVerifierCircuit definition

Configuration

Parameter	Value	Description
MAX_ROWS	256	Maximum rows in data matrix
MAX_COLS	16	Maximum columns in data matrix
MAX_GROUPS	32	Maximum group keys for SUM_BY
MAX_OPS	4	Operations per handler
MAX_HANDLERS	4	Number of handlers
N_LEVELS	3	Merkle tree levels (16^3 = 4096 leaves)

Usage

# Build
go build -o gnark-simple-verifier

# Run benchmark
go run main.go benchmark

# Compile circuit only
go run main.go compile

OpCodes

Code	Operation	Description
0	NOOP	No operation
1000	MERKLE16	16-ary Merkle root with mask
2000	COUNT	Count valid rows
2001	SUM_COL	Sum column with row mask
3000	SUM_COL_BY	Sum column grouped by another

Hash Function

This implementation uses Poseidon2 with a workaround for BN254 support in gnark v0.14.0:

• In-circuit: NewPoseidon2FromParameters(api, 2, 6, 50)
• Off-chain: bn254/fr/poseidon2.NewMerkleDamgardHasher()

Benchmark Results

Metric	Value
Constraints	4,426,200
Proof Time	~10.2s

Security Features

1. Strict opcode validation: Each operation must match exactly one valid opcode
2. Handler masking: Inactive handlers are skipped using mask multiplication
3. GROUP BY validation: SUM_BY fails if any row doesn't match a public group key
4. Result verification: Computed results must match public input results
5. StartIndex Support: HandlerStartIndex allows processing subsets of columns per handler

License

MIT